Persistence Of Vision Death Star

Death Stars were destroyed twice in the Star Wars movies and yet one still lives on in this 168 LED persistence of vision globe made by an MEng group at the University of Leeds in the UK. While Death Stars are in high demand, they mounted it on an axis tilted 23.4° (the same as the Earth) so that they can show the Earth overlaid with weather information, the ISS position, or a world clock.

More details are available on their system overview page but briefly: rotating inside and mounted on the axis is a Raspberry Pi sending either video or still images through its HDMI port to a custom made FPGA-based HDMI decoder board. That board then controls 14 LED driver boards mounted on a well-balanced aluminum ring. All that requires 75W which is passed through a four-phase commutator. Rotation speed is 300 RPM with a frame rate of 10 FPS and as you can see in the videos below, it works quite well.

It was done on a DSLR which was the only thing I had at the time (other than a phone) to record with, but it doesn’t have the option to change the frame rate/shutter speed in video. I’ve been meaning to make a better one, but the last couple of years I was working abroad so didn’t have access to the globe (I do now I’m back working at Leeds Uni), and to be fair I wasn’t expecting it to make the rounds again on blogs/twitter given we made it 3 years ago.

What you can do is up the exposure value (EV) to decrease the shutter speed and put an neutral density (ND) filter to darken it back down so that it doesn’t blow-out to white. Even a sunglasses lens can do the same job as an ND filter.
It’s the same process used to capture those “see of mist” seaside photos and flowing water/waterfall/stream photos.

Resistance is futile. Oh wait, that’s Star Trek. I did mention their using it for showing an Earth overlaid with weather information and the ISS position. I thought that was pretty cool. Made me wonder if somehow a second ring with larger diameter could be spinning outside the first so that the weather info and ISS could really be “over” the Earth.

(Leeds uni student here) It’s been knocking around the university for a few years now; Usually gets wheeled out for taster days etc. It’s a pretty nicely done chunk of kit, though; I liked the way they did the modular LED boards.